$HCl(aq)+H_2O(l)rarr Cu^(2+) + 2NO_3^-$
$Ca(OH)_2(s) stackrel(H_2O)rarr Ca^(2+) +2HO^-$
$Ca(NO_3)_2(s) stackrel(H_2O)rarr Ca^(2+) +2NO_3^-$
$NH_3(aq) +H_2O(l) rightleftharpoonsNH_4^+ + HO^-$
And one of these things is not like the other ones.........